An effective, quick-acting and quick-reversing means of blocking the conduction of action potentials in whole nerve would have many important clinical applications, such as the elimination of pain and the modulation of muscle spasticity. One potential method for achieving this type of nerve conduction block is to use high frequency alternating current delivered through electrodes surrounding the target nerve. In our currently funded project, we have determined that this method can block 100% of the motor response in motor nerves. The block is gradable and can be completely reversed within one second. We are now ready to take the next step toward practical clinical implementation of this technique. Therefore, the specific aims of the proposed project are to: 1) determine if the chronic block of nerve conduction is damaging to the nerve, 2) determine the specific parameters necessary to provide motor and sensory block in humans, and 3) complete the technical and regulatory effort necessary to proceed to widespread human application of this technique. Chronic nerve block will be applied to the peripheral nerves of dogs for four weeks using parameters and regimens based on anticipated human applications. The post-operative nerve histology will be the primary outcome measure that will be used to determine if there are any damaging effects of the chronically applied conduction block in-vivo. We expect that the conduction block will not damage peripheral nerve because it uses a very low charge delivery per phase and delivers a zero net charge to the tissue. In conjunction with the chronic animal study, we will commence acute human studies using: 1) explanted human nerves to determine the parameters necessary for conduction block in large diameter nerves, 2) acute intra-operative testing to determine if successful motor block can be accomplished in the presence of intact reflex circuits, and 3) short-term chronic experiments to determine the parameters necessary for complete pain block. At the end of the proposed three year project, we expect to have completed all of the necessary tasks to enable the application of electrical nerve conduction block in humans for the elimination of peripheral nerve pain and for the modulation of muscle spasticity. This research will provide a significant tool in our ongoing efforts to reduce disability and improve quality of life.